Liquid compass



Jan. 15, 1935. s. R. HARRIS ET AL LIQUID COMPASS Original Filed Nov. 17, 1950 INVENTORS \SAMUEL R. HARR/s. g HARVEY N. LuMM.

Patented Jan. 15, I935 Harvey N. Lumm, Dayton, Ohio Original application November 1'7, 1930, Serial No.

426,186, now abandoned. Divided and this application September 23, 1932, Serial No. 634,538

1 Claim.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates to liquid magnetic compasses and more in particular to certain improvements in the compass bowl.

It is a well-known fact that the liquid which serves in some degree to dampen the forced oscillations of the compass card that is suspended on a central pivot in the liquid contained in the bowl, under excessive vibrations of the compass becomes highly turbulent taking up a rotary motion and imparting to the compass card a deflection of considerable magnitude from its position of equilibrium.

The large number of instruments that are made use of in airplanes and the limited space on the instrument board as well as the maintaining of the weight of instruments at minimum make it highly desirable to obtain compasses in which the bowl size is a minimum consistent with the requirements for a sufficiently sensitive north seeking magnetic card and for a sufl'iciently large enough opening through which the usual meridian marks or points on the card may be observed.

It is, therefore, a primary object of our invention to provide a compass bowl with means whereby the rotary motion in azimuth of the dampening liquid set up as a result of vibration or relative rotary motion of the airplane and the magnetic leveling, is deflected whereby the speed of rotation is materially reduced.

A further object of our invention is to provide a liquid compass in which the liquidchamber and compensating magnet chamber are so constructed and arranged as to produce a bowl of relatively small overall dimension, and more in particular the overall dimension thereof in the vertical plane.

In the drawing:

Fig. 1 is a front elevational view of the compass bowl;

Fig. 2 is a sectional view taken on the line 22 of Fig. 1, with compass card removed and its support broken away; and

Fig. 3 is a perspective view of the compensating magnet carrier.

As illustrated herein, the compass bowl 10, which may be made of any light material, such as aluminum, phenol-formaldehyde condensation product or the like, is preferably made so that its internal form is substantially cylindrical, with the longitudinal axis thereof in a horizontal plane at right angles to the vertical axis of the compass card 12, so that advantage is taken of the flow of liquids (which is in the path of least resistance), and in this case, in the event of excessive vibrations of compass bowl, would tend to flow in a circular path at right angles consequence when the card is rotated than that arising as a result of tilt. I

The compass bowl 10 is provided with a horizontally disposed partition 14 to form two chambers 16 and 18, one above the other. Chamber 16 is provided with an opening in the front side of the bowl and is adapted to receive a compensating magnet carrier 20 whereas chamber 18 is provided with an opening also on the front side of the bowl and is adapted to receive magnet card and the liquid in which the card is suspended.

The liquid chamber opening is closed by a glass (not shown) through which the compass card may be observed. The glass is fitted within a recess 22 formed in the bowl and is secured therein by a clamping ring 24 that is attached by means of screws 26 to the peripheral edge of the liquid chamber. The ring 24 is preferably shaped in the form of a segment of a circle and is disposed :with the base thereof in the plane of the partition 14 so that it cooperates with a portion of the recess 28 formedin the bowl to provide an opening to receive a closure member 30. Suitable means (not shown) is provided for detachably securing the closure member in place. The ring 24 and closure 30 constitute a supporting boss or flange that is adapted to have interfitting engagement with an opening in the instrument panel (not shown).

The magnet carrier 20 is provided with two sets of spaced horizontally disposed drilled holes, one slightly above and at right angles to the other. These holes are of such dimension as to receive magnets having a strength of maximum requirements so as to compensate for outside influence tending to cause the magnetsof the compass card to deviate from the magnetic north.

The rear plate 34 of the bowl has threaded therein a compensating casing 36 for an expansion chamber in the form of a sylphon 38 to take care of the expansion and contraction of the fluid due to temperature changes. The liquid with which the compass bowl is filled may be varied as desired, but by way of illustration, it may be stated that this liquid is a mixture of alcohol and water.

The compass when mounted on the instrument panel (not shown) of the airplane is rigidly secured thereto by means of bolts and nuts (not shown) passing through the ears formed around the forward peripheral portion of the casing.

It is to be understood that the present disclosure of our. invention is by way of illustration, only, and is not restrictive thereof; the invention being susceptible to various modifications which would be within the spirit of our conception with. out departing from the scope of the ifollowing; claim. 1 I

application Serial No. 496,186, filed 1930, now abandoned.

November; 1%,;

What we claim as new and desire to secure by Letters Patent is:

A compass comprising a compass bowl having a liquid containing chamber, an opening on one side of said chamber to receivea transparent coveiia said" bowl; havinggaag horizont lly; i fip partitionabove said openingand forming with thewalls of said bowl a chamber for compensat- -torreceive a carrier for said compensating mag- This is a divisional applicatigk mi g g Jnets, the open ends of said chambers presenting front face of the bowl.

SAMUEL R. HARRIS. I-IARVEY N. LUMM. 

